High temperature lubricant and process of preparation



Patented July 27, 1937 UNITED STATES 2,088,452 PATENT OFFICE.

HIGH TEMPERATURE LUBRICANT AND PROCESS OF PREPARATION Irving R.Valentine, Erie, Pa., assignor to General Electric Company, acorporation of New York No Drawing. Application July 10, 1935, SerialNo. 30,637

8 Claims.

The present invention relates to lubricants and process of preparing thesame, and refers more both heat and pressure.

Y Heretofore lubricating greases have. been prepared by compoundingmineral oil and a soap such as sodium stearate, sodium oleate and sodiumpalmitate at low temperatures. The soap was compounded in the presenceof water, and a small percentage of water remained inthe final greasecomposition. In such a grease the soap holds the oil as a sponge. Whensubjected to heat, as is frequently encountered in service, the greasedecomposes and changes from a neutral or slightly alkaline compositionto one having distinctly acid characteristics. In.the decompositionprocess, the soap is destroyed causing an ultimate breakdown of thegrease. It appears that hydrolysis due to the presence of water in thegrease contributes materially to its instability.

The improved grease compositions embodying my present invention employ,inplace of water, analkyl ether of diethylene glycol, such as, themonoethyl ether of diethylene glycol. The alkyl ethers of diethyleneglycol act as a vehicle ior uniting the alkali and fat, or fatty acid inthe production of the soap constituent of the grease and apparently tosome extent combine with these reacting ingredients. The anhydrous soapcomposition thus formed, which contains a minor proportion of an alkylether of diethylene glycol, or a derivative thereof, is compounded witha suitable mineral lubricating oil.-

While various glyceride fats or oil, or fatty acids derived therefrom,or other saponifiable hydrocarbon, may be used in the formationof thesoap constituent, I prefer to employ a mixture of drying, semi-dryingand non-drying oils, the semi-drying oilvpreponderating over the otheroils. For example, with about one to ten parts of drying oil, and asimilar proportion of non-.

drying oil, I employ ten to fifty parts of a semidrying oil, such assoya bean oil.

A preferred process of preparing the lubricating grease is-as follows: amixture consisting of 3 parts sodium hydroxide, 10 parts monoethyl etherof diethylene glycol, and a vegetable oil mixture consisting of 2 partscastor oil, 3 parts tung oil, 2 parts raw linseed oil and 10 parts soyabean oil is heated gradually to 280 C. The latter threeoils have dryingproperties. The sodium hydroxide goes into solution at about 180 to 200C. and a soap is formed when the temperature of the mixture rises to therange between approximately 260 and 280 C.

My invention includes the employment ofother alkyl ethers of diethyleneglycol, such, for example, as the methyl or butyl ethers in place of theethyl ether of diethylene glycol.

The monoethyl ether of diethylene glycol,

which has a boiling point within a range of about 185 to 205 C., islargely evaporated during this heating step but a small amount stillremains in the composition either in its original state or else modifiedby chemical reaction. -In any event the residue remaining is capable ofacting as a bonding agent whereby such soap composition can be united oremulsified with mineral oil. Relatively large quantities of oil thus canbe held as a stable emulsion which does not break down during severeuse.

The mixture containing a small amount of an alkyl ether of diethyleneglycol and in addition some glycerine which is formed duringsaponification, is allowed to cool to approximately room temperature andthereupon the desired form of mineral oil is added.- For example, forheavy ball bearing grease, medium heavy oil of 10? F. cold test can beused. For special purposes requiring the greaseto remain plastic at lowtemperatures, lighter oil having a cold test of minus 40 F. may benecessary. In general the conditions under which the lubricating greaseis to be used will determine the character of the oil embodied in it.This oil and soap mixture in which mineral oil may constitute to percent of the total mass is heated to a temperature within the range ofabout 200 to 220 C.,until a clear solution is obtained. It is allowed tocool with constant stirring until the mixture thickens. If insolubleparticles, such as overcooked soap particles are present, they areremoved by filtration while the solution is hot and unthickened.

In some cases, a fatty acid such'as 'stearic acid may be incorporatedwith the other ingredients. For example, a mixture consisting of 30parts sodium hydroxide, parts monoethyl ether of diethylene glycol, 105parts stearic acid, and a vegetable oil mixture consisting of 4 partscastor oil, 6 parts tung oil, 4 parts raw linseed oil and 26 parts soyabean oil is heated gradually to 280 C. The sodium hydroxide goes intosolution at about 180 to 200 C. and the soap is formed when thetemperature of the mixture is between approximately 260- and 280 C. Theresulting anhydrous soap product which contains a small amount ofmonoethyl ether of diethylene glycol, some glycerine and perhaps otherdecomposition products is compounded with a chosen mineral oil asalready described.

The grease made in accordance with my invention is extremely stable andis particularly adapted for high temperature and high pressure Forexample, a grease composed of 1 part (12.5%)

soap prepared in accordance with the preferred p s and part 1 '7.5%)heavy medium min-.

era] lubricating oil had :the following characteristics: a

Before heat Alter heat treatment treatment for 90 hours at 126 C.

10 Melting point 136" 0. 135 0. Free N aOH. 193% 13% The addition or thehigh boiling dispersing agent, such as the monoethyl ether of diethylene5 glycol, performs at least two functions. First,

.it allows the alkali to go into solution at low temperature previous tothe formation of the soap, and secondly, while much of the alkyl etherof diethylene glycol is evaporated during the gradual temperature .rise,themixture still retains a small amount in a somewhat difierent formthat acts-as -a binding agent between the a mineral oil and soap. If analkyl ether of diethylene' glycol is not used, the soap is only capableof holding a small quantity of mineral oil,

the excess oilseparating as the temperature rises and the lubricatingproperties of the grease thus being destroyed. However,'when' analkylether of diethylene'glycol is used and a smallamount of an alkyl etherof diethylene glycol or derivative thereof remains as a bonding agentafter the I of the dispersing agent should remain in the mixture afterthe formation of the soap. The alkyl ethers of diethylene-glycol or thelikelost by evaporation may be reclaimed by condensa- J tion andusedagain.

Although I have illustrated my'preferred lu-' bricating grease employingcertain materials, my invention is not limited to thespecific-ingredients previously disclosed' Other alkalis' or mixtures ofthe same may be used in place of sodium hydroxide, such as potassiumhydroxide, calcium hydroxide and the like. However, as is well known tothe art, the physical properties or a grease, and its practical utilityfor a particular condition of lubrication, are dependent, among'- otherinfluencing factors, upon the particular al-' -kali or alkalis used inmaking the soap. As is commonly known, a grease containing a sodium soapof a particular fatty oil has a. higher melting point than agreasecontaining a calcium soap, or a mixture of calcium and sodiumsoaps of the same fatty oil. dlti'ons of lubrication'and for which aheat-resisting lubricant is required, greases containing sodi.-

- um soaps are therefore preferred. Varlousdry ing, semi-drying andnow-drying vegetable oils may also be employed. Where extreme pressurelubricants 'are desired the drying oils may be readily chlorinated orsulphurized.

herein are by weight.

All modifications obvious to those skilled in the art and coming withinthe true spirit and scope of my invention are meant to be covered in 75the claims appended hereto.

The boiling point of the dispersing agent use For high temperature con-What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

.diethylene glycol and vegetable oil, heating the reaction productsgradually to a temperature in i5 excess'of 180 C., cooling the mixture,and adding a preponderant proportion of mineral lubricating oil to thereaction products.

3. The process of making stable, high temperature lubricatinggrease'which comprises prepar- 20 ing anhydrous vegetable soap byreacting a non-1 aqueous mixture consisting of sodium hydroxide,

monoethyl ether of diethylene glycol and a mixture of vegetableoilscomprising castor, tung, linseed and soya bean oils, heating thereaction 25 products gradually to a .temperature of about 280 C.,cooling the mixture, adding a preponder ant'proportion of'minerallubricating oil to the. reaction products, and heating the mixture untila clear solution is obtained. 30 4 'minor proportion of an anhydrousalkali metal 40 soap prepared by heating to reaction temperature anon-aqueous mixture consisting of an alkali metal -hydroxide, fattymaterial, and 'an-alkyl e'ther of diethylene glycol.

6. A stable, heat-resisting alkali metal soap 45 grease consisting.essentially of-a major proportion of minerallubricating oil and aminor'proportion of an anhydrous alkali metalsoap com-. posed ofthereaction product of anon-aqueous mixture consistin f an alkali metalhydroxide,

drying and semi-drying oils, and-castor oil, and

suflicient alkyl ether of diethylene' glycol to leave in the product aresidue of same as a bonding agent. 4

7. A stable, heat-resisting alkali metal soap 55 -greaseconsistingessentially of a preponderant proportion'of minerallubricating oiland a minor proportion of an anhydrous alkali metal soapcomposed of the reaction product of a non aqueous mixture consisting ofan alkali 'metal 4301 hydroxide, stearic acid, drying and. semi-dryingvoils and castor oil, and suflicient alkyl ether of diethylene glycol toleave in the product a residue of same'as a bonding agent."

8. A stable, heat-resisting sodium-soap grease 65:

consisting essentially of at'least about 85 per cent mineral lubricatingoil and the-remainder consisting of an anhydrous sodium soap com-- posedof the reaction product of a non-aqueous All parts or percentageproportions mentioned mixture consisting of sodium hydroxide, stearicacid, castor oil, tung oil, linseed oil and scya bean as a bondingagent.

IRVING R.

